The present invention relates to a hexapodal machining center having a fixed frame and a support which are interconnected via six struts of an adjustable length.
Such hexapodal machining centers are used as machine tools. They are particularly suited for cutting machine tools, e.g., for milling, drilling, turning or grinding or for laser machining.
In principle, hexapodal machining centers consist of a support, which is sometimes designated as a working platform, and of a fixed frame which are interconnected by six struts of an adjustable length. This allows a movement of the working platform in all of the six spatial degrees of freedom, i.e., three translational degrees of freedom and three rotational degrees of freedom.
A first hexapodal machining center is known from U.S. Pat. No. 5,401,128. This known machine tool structure consists of an octahedral framework comprising twelve rigid struts. A machining unit comprising a spindle is arranged in the center of the framework. Furthermore, a fixed workpiece-receiving device is arranged in the lower part of the octahedral machine frame of the fixed workpiece-receiving device. The hexapod, i.e, a support or working platform for the machining unit, e.g., a drilling or milling spindle, is provided above the workpiece receiving device. Two respective struts of the hexapod which can be adjusted in their length are coupled with one end to a corner of a triangular upper frame part of the machine frame, the connecting points of the two struts on the machine frame being only slightly spaced apart with respect to their height. All of the connecting points of the six struts on the working platform are located in a joint plane. Such an arrangement limits the rotational movements. Moreover, the forces cannot be received in the struts in an optimum manner since these do not extend in the directions of the main load.
A further hexapodal machining center is known from U.S. Pat. No. 5,354,158. In the hexapod shown in that document, two neighboring struts are coupled at a comer of an imaginary triangle to the working platform and two other neighboring struts to the comer of a further imaginary triangle on the frame, the two triangles arranged in parallel with each other being rotated relative to each other. The connecting points of the struts on the working platform and on the frame are each arranged in a common plane. Moreover, it is known from U.S. Pat. No. 5,354,158 that the connecting points on the frame are arranged in two spaced-apart planes. Such an arrangement has similar shortcomings as the arrangement according to U.S. Pat. No. 5,401,128 with respect to the movability of the working platform and the force-receiving capacity.